1. Field of the Invention
This invention relates to dental impression trays and, more particularly, to a device for producing an impression of teeth in a mouth.
2. Description of the Prior Art
Impression trays for making impressions of teeth are generally well known. The impression trays are filled with dental impression material and pressed onto a section of the teeth or against the entire upper or lower teeth in the mouth. The impression material cures while in the mouth and when the material is fully cured the impression tray is removed from the mouth. The impression created is then used to form a model of the teeth during the formation of a dental restoration.
Impression trays which are presently used have a mouthpiece, of a shape conforming generally to the bite radius of teeth, with a handle extending out from a midsection thereof. Some of these trays have holes positioned throughout the walls of the mouthpiece, providing an anchoring surface for impression material, to permit the excess flow of impression material to attach thereto. Some have holes only along the sides of the mouthpiece and others have holes on both the sides and base of the mouthpiece. Other trays have no holes positioned throughout the walls of the mouthpiece but instead use adhesive to retain the impression material.
An example of a hole on the base of a mouthpiece, as is typically used in presently known impression trays, is shown in FIGS. 5a and 5b. As can be seen, the hole in FIG. 5a has the shape of an inverted funnel and the hole in FIG. 5b is cylindrical in shape. When making an impression, the impression material placed in the mouthpiece will be displaced through the small end of the hole 110 and pass through into the funnelled end of the hole 112. Further, the problem associated with these types of holes is that by seating the tray, typically two fingers are placed at the back of the tray base to guide the tray in its final position for curing of the impression material. These fingers block some holes so impressional material cannot flow through completely. In the case of FIG. 5a, there is a theoretical retaining body, i.e., the inverted funnel, in FIG. 5b there may be no retaining body at all. With the hole as shown in FIG. 5a, there is the disadvantage that when pulling the tray out of the mouth with the cured impressional material, forces occur that act on the retention ability of the funnel. Since rubber material has a high cross contraction if elongated, there is a danger of movement. This will distort the impression.
Furthermore, presently used impression trays made of plastic or brass tend to flex easily along its sides or legs. When the tray is inserted into a mouth, the pressure exerted on the legs, by the impression material, can cause the legs of the tray to spread and when force is applied to the outer side of the legs to remove the tray, the legs will flex. This motion in the legs of the tray causes the impression to be disfigured. Applying a force to the handle portion for releasing the tray from the mouth also causes the tray to bend, further distorting the impression.
Most presently used trays also prevent good aligning with a normal bite. These trays do not have a curvature to align with a normal bite radius. The presently used trays also cannot sit flatly on a surface when removed from the mouth, and have other structures which make their use difficult.
It is therefore needed to produce an impression tray which avoids the aforementioned problems and provides improvements and ease in the formation of dental restorations.